I spend a lot of time training. Even more than that, I spend a lot of time thinking about training. There's one rule I always come back to, the often forgotten golden rule of training, "Stimulate, Don't Annihilate."
Lee Haney I believe has credit for that quote, but it's what smart lifters have been doing forever. You can't train doing Mach 1 with your hair on fire (if you still have it) for extended periods of time. However, that's how most of us think we have to train to make progress.
Of course, you have to put the pedal to the metal while lifting. That said, you can't do it for every exercise for every rep. For the most part, the formula for success is doing some heavy work for low reps and some light work for high reps. As long as it wasn't easy and you make progressions in volume, you will improve.
Like a lot of my posts, this serves as a reminder to myself. I want to improve so badly that I feel like if I'm not killing myself in the gym, I'm not making progress. The truth is, especially with my age, when I kill it too often, I end up further back than where I started.
For most who have a good five-plus years under their lifting belt, we are not seeing 50 lb gains on our lifts over a training cycle. We are probably not even seeing that over the course of a year unless there's a significant gain in body weight or some high-grade pharmaceuticals.
Track your numbers for volume and keep an eye on RPE. Focus on recovery and make incremental improvements. That's how gains are made when you have been lifting for a while.